In general, fuel injection systems mix fuel with air in internal combustion engines. Fuel is forcibly pumped through a fuel injector resulting in atomization of the fuel which is then mixed with air and is either indirectly or directly placed in the combustion chamber. The fuel/air ratio must be precisely controlled to achieve desired engine performance, emissions, and fuel economy. Fuel injection systems react to changing inputs, where the inputs are data provided by various sensors, by controlling the amount of fuel injected.
An example of a known open loop electronic fuel injection (EFI) system is illustrated in FIG. 1. The open loop EFI system 10 is comprised of a fuel injector 12, an electronic control unit (ECU) 14, an air flow sensor 16, communication circuitry 18 linking the ECU 14 and the air flow sensor 16 and communication circuitry 20 linking the ECU 14 and the fuel injector 12. Other known components that are sometimes used in such systems, but are not shown in FIG. 1, include a fuel pump, a fuel pressure regulator, other input sensors, which may include but are not limited to, a hall effect sensor, a manifold absolute pressure (MAP) sensor, a throttle position sensor, a coolant temperature sensor, an oil temperature sensor, and a manifold air temperature (MAT) sensor.
A known closed loop EFI system is illustrated in FIG. 2. The components of the closed loop EFI system 40 are generally the same as that of the open loop EFI system 10 except for the addition of an oxygen sensor 42 located in the exhaust system 22. Communication circuitry 44 links the ECU 14 and the oxygen sensor 42.
Other common features of the engine systems shown in FIGS. 1 and 2 include an exhaust system 22, an intake system 24, the engine 26, an alternator 28, and a gas tank 30. Air flow 32 enters at the intake system 24 and exhaust flow 34 exits at the exhaust system 22. Fuel 36 moves from the gas tank 30 to the fuel injector and is atomized. The atomized fuel 38 enters the intake system.
In an open loop EFI system 10 (e.g., FIG. 1), an air flow sensor 16 (or other sensor(s) such as a MAP or MAT) senses the mass of air that flows past it and transmits this data to the ECU 14. The ECU 14 uses this data, along with the requested relative AFR to provide the correct fuel flow that will provide acceptable engine performance. The requested relative AFR is typically determined from a lookup table using various sensor input data, for example, sensor input data from an oil temperature sensor, from an engine speed sensor, or from other available sensors. The ECU 14 electrically actuates the fuel injector 12 so that the atomized fuel 38 mixes with the air flow 32 to reach the requested relative AFR as provided in the look-up table. Open loop EFI systems 10 do not receive any feedback as to whether the correct AFR is being achieved. The AFR may be incorrect due to degradation of the fuel injector 12, the air flow sensors 16 may be out of tolerance, etc. While an open loop EFI 10 is a lower cost system, the engine may not meet performance and emission requirements since there is not sufficient air/fuel mixture control to enable effective exhaust catalysis, resulting in unacceptable system performance. In general, engines that operate with strictly open loop EFI systems 10 are not used in automobiles, do not operate on fuel blends and are made to operate using only one grade, type or blend of fuel.
A closed loop EFI system 40 (e.g., FIG. 2), works in much the same way as the open loop EFI system 10 except for the addition of the oxygen sensor 42. The oxygen sensor 42 senses the amount of oxygen in the exhaust gas after combustion which is an indicator of whether the AFR is too lean or too rich for optimum combustion. Data regarding the oxygen levels is transmitted to the ECU 14, along with information from other sensors that may be available. The data is processed to determine the AFR so that the ECU 14 can thereby actuate the fuel injector 12 to adjust the amount of atomized fuel 38 injected, so that the air/fuel mixture matches the requested AFR.
During full throttle conditions, on initial start-up, or during a transient occurrence (such as a load suddenly applied to the engine) the ECU 14 may ignore inputs from the oxygen sensor 42, thereby mimicking an open loop state, so that the engine 26 can meet the required performance by running a richer mixture. In the case of initial startup, inputs from the oxygen sensor 42 may be ignored during the start-up phase until appropriate operating temperatures are reached, wherein the time from start-up to oxygen sensor 42 input reading can be delayed from several seconds to a couple of minutes, resulting in non-optimal engine performance. Closed loop EFI systems are known in the automotive industry.
In addition, some closed loop EFI systems 40 in the automotive industry incorporate alcohol sensors. This allows automobiles to operate on various blends of gasoline and ethanol, and also operate in the event the alcohol content is varied, for example, if ethanol is put into a tank that still contains gasoline. In general, fuel is added to the tank after the automobile is driven to a fueling station. In such a case, the oxygen sensors and alcohol sensors are typically operating in a hot or warm re-starting state, rather than a cold re-starting state of the engine, and adjustments to the AFR are done fairly quickly with a minimum of performance and efficiency issues. Engines that operate on fuels that have a wide range of ethanol and gasoline blends use closed loop control, with or without alcohol sensors, to provide the correct fueling so that the AFR is attained for acceptable performance.
However, it is not known in the automotive industry or in other engine applications to incorporate alcohol sensors into an open loop EFI system where different grades or types of fuels may be blended and used. There is a need for an open loop EFI system that incorporates alcohol sensors for other engine types, i.e., genset engines.